Maybe someone here will know the answer to this...
The game industry continues to complain about used games, correct? Gamestop is the big used game people, costing the game industry tens, if not hundreds of millions of dollars, correct (I'm referring to direct losses, not here for a debate as to whether used games are good or not)?
So why do game companies give big boosts like this to companies like Gamestop? If a new gamer has always bought their stuff at Best Buy and sees this offer, they'll head on over to Gamestop. You just gave Gamestop a shiny new customer who may or may not have realized how much cheaper all these used games are compared to the new ones he keeps buying.